As a battery to be mounted in an electric car, a hybrid car, etc., there is known an assembled battery obtained by connecting a plurality of battery cells such that positive and negative electrodes thereof are connected in series (for example, see PTL 1). Such an assembled battery is characterized in having high output and high energy density. In most cases, lithium ion batteries are used as the battery cells. In a lithium ion battery, a plus output terminal is formed of aluminum (Al), and a minus output terminal is formed of copper (Cu).
A bus bar (a component used to distribute electric energy) is a component that connects terminals of such battery cells. As a production method for such a bus bar, for example, members that constitute the bus bar are subjected to laser beam welding, as disclosed in PTL 2.